1. Overview of Receptors and Drugs
By Kevin Mikielski, D.O.
Department of Cardiology

2. Receptors and Actions

3. Receptors and Actions Alpha 1 Beta 1 Beta 2
Present on peripheral vasculature
Stimulation results in vasoconstriction
Beta 1
Present in myocardium and conduction system
Stimulation results in enhanced contractility, heart rate and speed on conduction in electrical system of heart
Beta 2
Present in skeletal muscle, lung and vasculature
Stimulation results in vasodilatation and bronchodilatation

4. Specific Drugs EPINEPHRINE Stimulates Alpha 1 Stimulates Beta 1
Vasoconstriction
Stimulates Beta 1
Increases contractility, heart rate and conduction
Overall effect is to increase cardiac output
Stimulates Beta 2
Vasodilates
Bronchodilates
Will increase cardiac output through Beta 1; Usually will increase blood pressure due to Alpha 1>Beta 2

5. Norepinephrine Norepinephrine Stimulates Alpha 1 Stimulates Beta 1
In general, this is its major site of action and its major clinical use
Stimulates Beta 1
Stimulates Beta 2

6. Dopamine
Dopamine
Actions are dose-dependent but wide variation/range of effects are seen
1-5 mcg/kg/min
Stimulates dopamine receptors
Increased renal blood flow
Has NEVER been shown to have clinical benefit and “Renal dose dopamine” should not be used

7. Dopamine (continued) 5-10 mcg/kg/min 10-20 mcg/kg/min
Primarily stimulates Beta 1 receptors
10-20 mcg/kg/min
Primarily stimulates Alpha 1 receptors
Great amount of overlap between doses and effects

8. Dobutamine Dobutamine
Stimulates Beta 1 and 2 receptors
Not a good drug for hypotension unless the etiology is severe LV dysfunction, acute MI with cardiogenic shock, or acute pulmonary embolism where hypotension will improve with increased cardiac output
Usually will decrease blood pressure due to Beta 2 effects

9. Phenylephrine / Vasopressin
Phenylephrine (Neosynephrine)
Stimulates Alpha 1 receptors
No Beta effect
Vasopressin (ADH)
Stimulates V1 receptors and acts similar to Alpha 1 agonists, but exact mechanisms of vasoconstriction are not completely understood
Cautious use in patients with ACS and CHF because it can result in coronary spasm and volume retention

10. Adenosine / Atropine Adenosine Atropine
Acts via Adenosine 1 receptor in conduction system to slow heart rate/SA/AV block
Need to give rapidly as bolus followed by flush due to ½ life of only 6 seconds
Atropine
Acts to inhibit AcH effects on conduction system
Increases sinus rate and AV nodal conduction
Does not directly increase blood pressure

11. Thank you for your attendance.
End of Lecture
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